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  1. JDK
  2. JDK-8277543

Implement PAC-RET branch protection on Linux/AArch64

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Details

    • CSR
    • Status: Closed
    • P4
    • Resolution: Approved
    • 19
    • hotspot
    • None
    • low
    • Could not find any existing use of UseBranchProtection anywhere. The flag is intentionally similar to the GCC/Clang flag -mbranch-protection.
    • add/remove/modify command line option
    • Implementation

    Description

      Summary

      Add a command line option to enable/disable AArch64 PAC-RET. This should flag should be expandable for future branch protection work. GCC/Clang already has a -mbranch-protection flag which supports PAC-RET and BTI. Where possible we should following existing precedents.

      Problem

      AArch64 PAC-RET support needs the ability to enable or disable it.

      Solution

      Add XX:UseBranchProtection string flag for AArch64.

      Specification

      -XX:UseBranchProtection will have the following options:

      • none - Disable PAC-RET support. This is the default option.
      • standard - Enable PAC-RET support if the system supports it and the java binary was compiled with PAC-RET. Otherwise disable PAC-RET.
      • pac-ret - Enable PAC-RET support. If the system does not support it or the java binary was not compiled with PAC then print a warning but leave enabled.

      If/When BTI or other branch protection functionality is added, then additional options can be added. The option to concatenate multiple options together should be added (for example bti+pac-ret). Standard should always enable all options that are available for the current system.

      pac-ret will initially only supported on AArch64 Linux.

      For reference, the GCC supports: -mbranch-protection=none|standard|pac-ret[+leaf+b-key]|bti And allows multiple options concatenated together via +

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              ahayward Alan Hayward
              ahayward Alan Hayward
              Andrew Haley, Daniel Daugherty, Ningsheng Jian
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              Dates

                Created:
                Updated:
                Resolved: